Here we have an argument. The conclusion is the last sentence, i.e. "Therefore, this discovery provides definitive evidence that schizophrenia is caused by damage to the physical structure of the brain." What is this discovery? When the brains of identical twins, which are genetically identical, are compared and only one is a schizophrenic, certain areas of the affected twin's brain are smaller than corresponding areas in the brain of the unaffected twin. These differences are absent when neither twin is a schizophrenic.
The question stem is asking us to find the answer choice that CANNOT BE TRUE. So the four incorrect answers choices here are possible, while the correct answer will directly contradict some information provided in the stimulus.
Let's take a look at the answer choices:
(A) could be true because we are given no information in the stimulus regarding people who lack a genetic susceptibility for schizophrenia.
(B) could be true because we are given no information in the stimulus regarding medication and its ability to control and/or cure schizophrenia.
(C) could be true because we only know that certain areas of the brain of those affected with schizophrenia are smaller but they could otherwise share many of the characteristics with the brains of those people without the disorder.
(D) CANNOT BE TRUE because it directly conflicts with the information in the passage. We are told that the brains of these identical twins were genetically identical. Therefore, on the basis of genetic information alone, it would not be possible to determine whether or not someone will develop schizophrenia. As such, (D) is the correct answer.
(E) could be true because we are given no information in the stimulus as to what can cause this damage to the physical structure of the brain.
Hope this helps! Please let us know if you have any other questions.
awashingNovember 14, 2016
Could you further go into why choice D is correct? Eventually was the word that threw me off in D as without the information given, how am I supposed to determine just off of the passage alone whether that could be true/could be false. Are you also inferring in your explanation that D conflicts with the conclusion, that "definitively" schizophrenia is caused by damage to the physical structure of the brain (i.e., genetic information has nothing to do with the source of the disorder?)
MehranNovember 15, 2016
@awashing of course! Sorry for the confusion here.
(D) states, "It will eventually be possible to determine whether or not someone will develop schizophrenia on the basis of genetic information alone."
This directly conflicts with the information in the passage because if schizophrenia were caused solely by genetics, identical twins, who are genetically identical, would either both have schizophrenia or neither would.
The author cites an example in which only one of a pair of identical twins is schizophrenic and uses this to conclude that schizophrenia is caused by damage to the physical structure of the brain, i.e. not on the basis of genetic information alone.
Hope this helps! Please let us know if you need further clarification.
Madelyn-LuskeyJuly 11, 2018
Could (D) also not be true given the conclusion that states, "....definitive evidence that schizophrenia is caused by damage to the physical structure of the brain"? Is this basically proving that (D) cannot be true?
ChristopherJuly 28, 2018
@Madelyn-Luskey, yes, that is part of the reason why (D) is the correct answer.
ThaliaFebruary 25, 2020
Hey there, I understand why D contradicts the passage. But could you go into further detail as to why the same cannot be said about A? Since it was established that genetics do not play a role here (i.e. twins), can't we also conclude that choice A cannot be true since genetics is a non-factor? Is that stretching the argument a bit too far? Thanks.
RaviMarch 19, 2020
@Thalia, happy to help. Let's look at (A). With (A), the argument's premises do not provide us with any information about the causes of schizophrenia, so it could be true that without genetic susceptibility, schizophrenia is impossible. Thus, (A) could be true, so it's not the right answer choice.
Does this make sense? Let us know if you have any other questions!
